what is the best way/sites to look for this kind of work to English-speaking company in Poland.
The best way, in Poland, just as everywhere else, is by word of mouth from the contacts in your personal network. The best jobs are never advertised, and all you will find with recruiters and internet job sites are the table scraps. Real jobs at real pay are recommended by real people in the real world, face to face, or "friend of a friend".